Method and apparatus for monitoring potential or lost circulation in an earth borehole

ABSTRACT

Method and apparatus for monitoring potential blowouts or lost circulation in a well by employing sensing devices on the drilling fluid pump and the well bore return pipe for the drilling fluid. Means are provided for monitoring the drilling fluid pumped into the well bore and for sounding a warning if a certain amount of drilling fluid flows out of the well bore before a minimum amount of drilling fluid is pumped into the well bore. Means are also provided for sounding the warning if no drilling fluid flows out of the well bore and the certain maximum amount of drilling fluid has been pumped into the well bore.

United States Patent [72] Inventors William A. Rehm;

Phil H. Griffin, III; Martin J. Sharki, all of Houston, Tex.

[21] Appl. No. 873,337

[22] Filed Nov. 3, 1969 [45] Patented Oct. 19, 1971 [73] AssigneeDresser Industries, Inc.

Dallas, Tex.

[54] METHOD AND APPARATUS FOR MONITORING POTENTIAL OR LOST CIRCULATIONIN AN EARTH BOREHOLE 8 Claims, 1 Drawing Fig.

[52] US. Cl. 340/239, 73/155, 166/250, 175/48, 235/92 FL, 417/43,417/63, 417/278 [51] lnt.Cl ..G08b 21/00 [50] Field of Search 340/239;

166/53, 54, 64, 75, 250; 175/24, 25, 48, 65; 73/151,153,I55;235/92 FL;417/43, 63, 278

FLOW SENSOR [56] References Cited UNITED STATES PATENTS 2,290,179 7/1942Hayward 175/48 X 3,198,250 8/1965 Hoch et al. 166/250 ABSTRACT: Methodand apparatus for monitoring potential blowouts or lost circulation in awell by employing sensing devices on the dri1ling fluid pump and thewell bore return pipe for the drilling fluid. Means are provided formonitoring the drilling fluid pumped into the well bore and for soundinga warning if a certain amount of drilling fluid flows out of the wellbore before a minimum amount of drilling fluid is pumped into the wellbore. Means are also provided for sounding the warning if no drillingfluid flows out of the w =1] bore and the certain maximum amount ofdrilling fluid has been pumped into the well bore.

VOLTAGE SOURCE CLUSIVE GATE COUNTER LOW SET POINT HIGH SET POINTPATENTEUUET I9 I97! 3 6 l 4. 761

MARTIN J. SHARKI :L PHIL H. GRIFFIN Ill WILLIAM A. REHM /MwM ATTORNEYMETHOD AND APPARATUS FOR MONITORING POTENTIAL OR LOST CIRCULATION IN ANEARTH BOREHOLE BACKGROUND OF THE INVENTION In drilling a well for oil,gas, water, and the like the drilling bit is supported in the well boreby tubing. The tubing is hollow pipe composed of a plurality ofindividual lengths (stands) of pipe connected together. The tubingcarries drilling fluid in its interior down to and through the drillingbit. The drilling fluid at the bottom of the well bore passes upwardlyin the annulus between the exterior surface of the tubing and theinterior surface of the well bore to the surface of the earth and thenthrough a return pipe to storage pits on the surface of the earthcommonly referred to as mud pits. The weight of the drilling fluid inthe well bore helps maintain a high pressure at the bottom of the borethereby preventing the intrusion into the bore of undesired lightermaterials such as gas, water, and the like. This is desirable becausethe intrusion of these materials forces drilling fluid from the wellbore through the return pipe and a dangerous and expensive blowout canoccur because of the reduced pressure in the bore.

Also, when drilling a well a paru'cularly porous geologic formation canbe encountered into which is lost substantial amounts of drilling fluid.This is a lost circulation situation which can be expensive and harmfulto the overall drilling operation.

oftentimes during the drilling operation the drilling bit becomes wornand has to be replaced. This calls for removing all of the tubing fromthe well bore. When tubing is removed from the well bore a very greatrisk of a blowout is run since the drilling fluid liquid head in thewell bore is shortened by the withdrawal of the tubing and the volumeconsumed in the well bore by that tubing. Therefore, the pressure at thebottom of the well bore is substantially reduced thereby causing thedanger of a blowout.

Normally the process followed when removing tubing from the well bore isto first calculate by conventional procedures well known in the art thevolume of drilling fluid needed to fill the volume vacated in the wellbore by each stand of tubing. One or more stands of tubing are thenwithdrawn from the well bore and the withdrawal of tubing stopped. Thewell bore is then filled with the volume of the drilling fluidcalculated to be necessary to fill the volume vacated by the stands oftubing withdrawn. Then one or more additional stands of tubing arewithdrawn and the process repeated until all the tubing is removed fromthe well bore.

It is during this process that it is extremely desirable to have as muchforewaming as possible against a potential blowout. It is also desirablyto have a warning of a lost circulation problem.

It is also helpful to have similar warnings when the tubing carrying thenew drilling bit is replaced in the well bore.

SUMMARY OF THE INVENTION According to this invention, there is providedapparatus for warning against potential blowouts or lost circulationproblems by employing warning means which take signals from the pumpwhich pumps drilling fluid from the mud pits into the tubing and fromflow sensing means on the outlet pipe which carries drilling fluid fromthe annulus between the exterior of the tubing and the interior of thewell bore to the mud pits.

The method of this invention comprises in its improved aspect thedetermination of minimum and maximum tolerable amounts of drilling fluidto be pumped into the well bore to compensate for the withdrawn tubing,measuring the amount of drilling fluid actually pumped into the wellbore, and sounding a warning when certain situations as hereinafterdefined are sensed bases upon pumping of the drilling fluid into thetubing and/or flow of drilling fluid from the well bore to the mud pits.

This invention also includes apparatus for use when tubing is beingreinserted into the well bore which employs timing means which receivesa signal from a flow sensor on the outlet pipe of the well bore andwhich is also operatively connected to a warning means. Thecorresponding method for this aspect of the apparatus of this inventioncomprises, in its improvement, the determination of the amount ofdrilling fluid to be displaced from the well bore by the amount oftubing to be reinserted in the well bore, measuring the amount ofdrilling fluid actually displaced from the well bore, and sounding awarning if more than the determined amount of drilling fluid is actuallydisplaced from the well bore.

Accordingly, it is an object of this invention to provide a new andimproved method and apparatus for monitoring the drilling of a well. Itis another object to provide a new and improved method and apparatus formonitoring a well for a potential blowout or lost circulation problemwhile removing tubing from the well bore. It is another object toprovide a new and improved method and apparatus for monitoring apotential blowout or lost circulation problem when tubing is beinginserted into the well bore.

Other aspects, objects, and advantages of the invention will be apparentto those skilled in the art from the disclosure and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION The drawing shows a systemembodying this invention.

More specifically, the drawing shows a well bore 1 lines withconventional casing 2 and having tubing 3 inserted therein therebydefining annulus 4 between tubing 3 and easing 2. Annulus 4 isoperatively connected with the interior of outlet pipe 5.

Pipe 5 conducts returning drilling fluid from annulus 4 to drillingfluid storage pit 6.

As additional drilling fluid is needed, it is removed from pit 6 by pump7 through line 8 and into tubing 3 to travel downwardly through tubing 3to the bottom of the tubing and the drilling bit at the bottom of theborehole (not shown).

Pump 7 is a conventional piston-type reciprocating pump which pumps aknown volume of liquid each time the piston passes through onereciprocation cycle, i.e., movement forward to the full extendedposition and then movement backward to the original starting position.This known volume is provided by the manufacturer of the pump so thatthe number of reciprocation cycles (pump strokes) of the pump requiredto deliver a desired volume of drilling fluid can be readily ascertainedin a conventional manner well known in the art.

Pump 7 carries a sensing device such as a microswitch which willregister each reciprocation cycle of the pump piston. A signalrepresentative of each reciprocation cycle is passed by electrical line15 to a conventional electronic device well known in the art as anexclusive OR gate the function of which is described hereinafter.

Gate 13 can be electromechanical, e.g., through the use of conventionalrelays, or can employ solid-state circuits whichever is desired by thoseskilled in the art.

Gate 13 is operably connected by way of electrical line 18 to aconventional counter 19 which is used for totaling the number ofreciprocation cycles registered by switch 14. Suitably counters arecommercially available and well known in the art. For example, asuitably counter is the Unipulser, type 49000-405, manufactured byDurant Company of Milwaukee, Wisconsin.

Counter 19 is operated by its own voltage source 28 which is connectedto counter 19 by way of electrical line 29. A signal from counter 19actually comes from voltage source 28 and not from gate 13 and is passedby electrical line 20 to low set point device 21.

The low set point device is a commercially available and well knowndevice. A suitably device is the Uniset Switch, type 40 500-400,manufactured by Durant Company of Milwaukee, Wisconsin.

Low set point device 21 is operably connected by'way of electrical line22 to a high set point device 23 which can be the same device as device21 except that it is used to register a maximum total of reciprocationcycles of pump 7 rather than a minimum total of reciprocation cycles ofpump 7 which is the function of low set point device 21.

Device 21 is also operably connected by way of electrical line 24 to aconventional AND gate the function of which will also be describedhereinafter. Gate 17, like gate 13, is a conventional piece of apparatuswell known in the art and can employ either electromechanical relays orsolid-state circuits as desired.

High set point device 23 is operably connected by 'way of electricalline 26 to a warning device 27. Gate 17 is also operably connected byway of electrical line 25 and line 26 to warning device 27.

Warning device 27 can be any device desired such as a horn, whistlelight, and the like.

A conventional flow sensor switch 9 is operably mounted on pipe 5 with apaddle means extending down into the interior of pipe 5 to sense thepresence of flow, if any, of the drilling fluid 'in pipe 5; Forexample,.if the flow starts, paddle 11 is moved toward the outlet endnearest pit 6 whereas if the flow stops, paddle 10,.being spring biasedin that direction, moves towards the inlet end of pipe 5 in casing 2.

The electrical signal output of flow switch 9 is carried by way ofelectricallines 11 and 16 to gate 17.

Between lines 1 1 and 16 there is operably connected a conventionalswitch means 30 which can divert the signal in line 11 from line 16 toline 31 and timer 32. Timer 32 can be any conventional apparatuscommercially available and known in the art such as the Time DelayRelay, type TDO-62C30-l A, produced by Guardian of Chicago, Illinois.

Timer 32 is operatively connected by way of electrical lines 33, 25, and26 to warning device 27.

Gate '13 receives intermittent signalsfrom switch 14, each signal beingrepresentative of one reciprocation cycle of pump 7 and therefore alsobeing representative of the pumping of a finite and know volume ofdrilling fluid into tubing 3 and into the well bore. Gate 13 is anexclusive OR gate because it passes the intermittent signals from switch14 to counter 19 so long as it does not receive a signal from flowsensor 9 by way of electrical lines 11 and 12. If a signal is receivedby gate 13 from flow sensor 9 it will stop passing signals from switch14 on to counter 19 and thereby stop the operation of counter 19 in itsfunction of totaling the number of reciprocation cycles of pump 7. Thus,gate 13 will pass signals received from switch 14 as long as no signalis also received from flow sensor 9 and when a signal is received fromsensor 9 the operation of the system is stopped by gate 13.

The current from source 28 passes through counter 19 and through device21 to either gate 17 or device 23. When the total reciprocation cyclesregistered by counter 19 is less than the low set point on device 21,the signal from source 28 is passed to gate 17. When the totalreciprocation cycles registered by counter 19 exceeds the low set pointon device 21, the signal from source 28 is not passed to gate 17 byrather is passed to device 23 instead. Device 23 does not pass thesignal on to warning device 27 unless and until the total number ofreciprocation cycles registered by counter 19 exceeds the high set pointon device 23.

Gate 17, when receiving a signal from device 21 will not pass thatsignal on to warning device 27 unless and until a signal is receivedfrom flow sensor 9 by way of lines 1 1 and 16. Thus, this gate is an ANDgate because it will not pass a signal on to warning device 27 until itreceives signals from both device 21 and flow switch 9.

If the total number of reciprocation cycles registered by counter 19 isless than the low set point on device 21, the signal from source 28 ispassed to gate 17 and not to device 23. In this situation if a signal isreceived from flow switch 9, gate 17 will pass the signal on to warningdevice 27. If the total number of reciprocation cycles registered bycounter 19 exceeds the low set point on device 21 the signal from source28 is not passed to gate 17 but ratheris passed to device 23 which doesnot'pass the signal on to warning device 27 unless and until the totalnumber reciprocation cycles registered by counter 19 exceeds the highset point on device 23.

Thus; when the total number of reciprocation cycles registered oncounter 19 (which is representative of the total number of pumpingstrokes of pump 7) is less than the lower set point on device 21 warningdevice 27 is not actuated unless a signal is also received from flowsensor 9 in which case a waming'device is actuated.

When the total number of reciprocation cycles on counter 19 is greaterthan the low set point on device 21 but less than the high set point ondevice 23, warning device 27 is not actuated.

When the total number of reciprocation cycles on counter 19 is greaterthan the high set point on device 23, warning device 27 is actuated.

In operation in the situation wherein tubing 3 is being withdrawn fromthe well bore and the number of stands of tubing that are to bewithdrawn at each step is known and the volume of drilling fluid neededto till the volume of the well bore vacated 'by the withdrawn tubing hasbeen calculated together with the number of reciprocation cycles of pump7 needed to supply this calculated volume of drilling fluid, the numberof stands of tubing upon which the calculations were based are withdrawnfrom the well bore and the withdrawal of tubing 3 is stopped.

The low set point on device '21 and the high set point on device 23 areset to bracket the number of reciprocation cycles calculated to benecessary for pump 7 to deliver to the well bore the volume'of drillingfluid calculated to be necessary to fill the volume vacated by thewithdrawn stands of tubing. It is preferable that the calculated numberof reciprocation cycles for pump 7 be employed as the low set point fordevice 21 so that a warning is given as soon as'the calculated number ofreciprocation cycles is exceeded thereby giving the very earliestadvance warning. The high set point for device 23 can be set at anynumber of reciprocation cycles higher than the calculated number ofreciprocation cycles, e.g., 10 per cent higher. This maximum set pointis an arbitrary set point and can be less than l0 percent or more than10 percent higher than the calculated number of reciprocation cycles.Pump 7 is started to pump drilling fluid into tubing 3 to fill the wellbore.

If during during the withdrawal of tubing from the borehole, there is animpending blowout, alien fluid will intrude into the borehole and thisintrusion will cause the total number of reciprocation cycles of pump 7to fill the borehole with less than the calculated number. In thissituation, the total number of reciprocation cycles registered oncounter 19 will be less than the low set point on device 21 and thesignal from source 28 will be applied to gate 17. Also in this situationliquid will flow from annulus 4 through pipe 5 before it wouldordinarily since annulus 4 is prematurely full because of the intrudingalien fluid. The annulus is thus filled while pump 7 is pumping. Thus,paddle 10 will be deflected toward the outlet end of pipe 5 adjacent pit6 beyond its set point and will cause a signal to be passed from flowswitch 9 through lines 11 and 16 to gate 17. When a signal is receivedby gate 17 from flow switch 9 and at the same time receives a signalfrom source 28, the gate will open and pass a signal to device 27thereby sounding a warning of an impending blowout.

If there is no impending blowout while pump 7 is being operated to fillthe well bore, the total number of reciprocation cycles registered bycounter 19 will reach or exceed the low set point on device 21 therebycausing the signal from source 28 to be switched from gate 17 to highset device 23. During this situation if a signal is received from flowsensor 9 caused by the flow of liquid through pipe 5 and deflection ofpaddle 10 past its set point toward the outlet end of pipe 5 adjacentpit 6, a signal is passed to gate 17 but since a signal from source 28is not also imposed on gate 17 by way of line 24, no signal is passed onto warning device 27. instead, the signal from flow sensor 9 passes togate 13 by way of line 12. When gate 13 receives the signal from flowsensor 9 it will stop passing signals from switch 14 on to counter 19thereby stopping counter 19 and the operation of the system. This samestoppage of counter 19 by impressing a signal from flow switch 9 on gate13 by way of line 12 occurs when a signal is imposed on gate 17 by wayof line 24 but in this case, even though counter 19 is stopped by gate13, the signal from source 28 is passed through gate 17 to actuatewarning device 27. However, in the present situation wherein the totalnumber of reciprocation cycles on counter 19 exceeds the low set pointof device 21 so that the signal of source 28 is not imposed on gate 17but rather is imposed on device 23, the

reception of a signal from flow switch 9 at gate 13 merelystops counter19 and therefore operation of the system without actuating warningdevice 27.

If the total number of reciprocation cycles on counter 19 exceeds thelow set point on device 21 and then goes on to exceed the high set pointof device 23, the signal from source 28 is then passed to warning device27 to actuated same because this indicates an unduly large amount ofdrilling fluid has been pumped into tubing 3 without filling the annulusand causing a consequent flow of liquid in pipe 5. If a flow of liquidhad been achieved in pipe 5 before reaching the high set point of device23, flow switch 9 would have passed a signal to gate 13 thereby stoppingthe operation of counter 19 and trapping the signal from source 28 indevice 23. However, when the total number of reciprocation cycles oncounter 19 exceeds the high set point on device 23, warning device 27 isactuated and in this instance warns of a lost circulation problem sincemore than the calculated amount of drilling fluid has been pumped intotubing 3 without liquid flow in pipe 5.

In operation wherein tubing 3 is being reinserted into the well bore,switch 30 is switched so as to pass signals from flow switch 9 in line11 to line 31 instead of to lines 12 and 16. It is determinedempirically by actual experience how long drilling fluid should bedisplaced from the annulus and should flow through pipe 5 when a singlestand of tubing is inserted into the well bore. in this manner, the timeperiod of drilling fluid flow in pipe 5 is known and timer 32 is set torun for this time period. Flow switch 9 is set to indicate liquid flowin pipe 5 toward the outlet end of pipe 5 adjacent pit 6 in a shortorder so that timer 32 can be started running as soon as there is flowin pipe 5. It should be noted that timer 32 runs only while flow sensor9 indicates liquid flow and if liquid flow in pipe 5 stops, therebyallowing paddle to move to its normal position, timer 32 also stopsrunning and is reset to zero time.

Thus, when flow sensor 9 first indicates liquid flow in pipe 5 timer 32starts running. If the drilling fluid flow in pipe 5 runs longer thanthe time period set for timer 32, timer 32 times out and passes thesignal from flow sensor 9 through lines 33, 25, and 26 to warning device27 thereby sounding a warning. This warning indicates that there isintrusion of alien fluid in the well bore and that this intrusion ispushing the drilling fluid out of the annulus in amounts greater thanthose amounts normally displaced by the tubing being inserted into thewell bore.

If the drilling fluid stops before timer 32 times out no warning issounded because flow sensor 9 stops indicating liquid flow in pipe 5before timer 32 times out.

Thus, impending blowouts are warned of when tubing 3 is being reinsertedinto the well bore as well as when that tubing is being withdrawn fromthe well bore.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. ln apparatus for monitoring potential blowouts and lost circulationin a well wherein a conduit means returns drilling fluid from the wellbore and a reciprocating pump means transfer drilling fluid to said wellbore, the improvement comprising in combination liquid-flow-sensingmeans operatively connected to said conduit means, means for registeringeach reciprocation cycle of said pump means, counter means for totalingthe number of reciprocation cycles registered by said registrationrneans, means for setting minimum and maximum totals of reciprocationcycles, warning means, and gate means for actuating said warning meanswhen one of the following occurs:

1. the total number of reciprocation cycles is less than the set minimumand liquid flow is sensed by said liquid-flowsensing means, and

2. the total number of reciprocation cycles exceeds the set maximum andno liquid flow is previously sensed by said liquid-flow-sensing means.

2. The apparatus according to claim 1 wherein timer means is operativelyconnected between said liquid-flow-sensing means and said warning means,and switch means for electrically isolating said timer from theapparatus of claim 1.

3. The apparatus according to claim 2 wherein said timer means startsrunning when the signal is received from said liquid-flow-sensing meansand continues to run as long as said signal is received but stops whensaid signal is no longer received so that the signal is not passed on tosaid warning means if said signal stops before said timer times out.

4. The apparatus according to claim 1 wherein said gate means comprisesan AND gate operatively connected between said means for setting saidminimum reciprocation cycles total and said warning means, and anexclusive OR gate operatively connected between said means forregistering each reciprocation cycle and said counter means so that saidAND gate receives a signal from said counter means so long as the totalreciprocation cycles counted by said counter means is less than the setminimum but does not pass said signal or unless and until a signal isalso received from said liquid flow sensing means, and said exclusiveOR" gate receives signal pulses from said means for registering eachreciprocation cycle and passes same on to said counter means unless anduntil a signal is received from said liquid-flow-sensing means.

5. The apparatus according to claim 3 wherein said means for registeringeach reciprocation cycle is a microswitch carried by said pump means.

6. A method for monitoring potential blowouts and lost circulation in awell wherein drilling fluid is pumped into the well bore, theimprovement comprising determining minimum and maximum tolerably amountsof drilling fluid to be pumped into said well bore, measuring the amountof drilling fluid ac tually pumped into said well bore, sounding awarning if drilling fluid flows out of said well bore before said setminimum amount of drilling fluid is pumped into said well bore, andsounding a warning if no drilling fluid flows out of said well bore andsaid set maximum amount of drilling fluid has been pumped into said wellbore.

7. The method according to claim 6 wherein said method is employed whenremoving tubing from the well bore.

8. The method according to claim 7 wherein when tubing is being insertedin said well bore, determining the amount of drilling fluid to bedisplaced out of the well bore by the amount of tubing to be inserted,measuring the amount of drilling fluid actually displaced, and soundinga warning if more than the determined amount of drilling fluid isactually displaced from said well bore.

1. In apparatus for monitoring potential blowouts and lost circulationin a well wherein a conduit means returns drilling fluid from the wellbore and a reciprocating pump means transfer drilling fluid to said wellbore, the improvement comprising in combination liquid-flow-sensingmeans operatively connected to said conduit means, means for registeringeach reciprocation cycle of said pump means, counter means for totalingthe number of reciprocation cycles registered by said registrationmeans, means for setting minimum and maximum totals of reciprocationcycles, warning means, and gate means for actuating said warning meanswhen one of the following occurs:
 1. the total number of reciprocationcycles is less than the set minimum and liquid flow is sensed by saidliquid-flow-sensing means, and
 2. the total number of reciprocationcycles exceeds the set maximum and no liquid flow is previously sensedby said liquidflow-sensing means.
 2. the total number of reciprocationcycles exceeds the set maximum and no liquid flow is previously sensedby said liquid-flow-sensing means.
 2. The apparatus according to claim 1wherein timer means is operatively connected between saidliquid-flow-sensing means and said warning means, and switch means forelectrically isolating said timer from the apparatus of claim
 1. 3. Theapparatus according to claim 2 wherein said timer means starts runningwhen the signal is received from said liquid-flow-sensing means andcontinues to run as long as said signal is received but stops when saidsignal is no longer received so that the signal is not passed on to saidwarning means if said signal stops before said timer times out.
 4. Theapparatus according to claim 1 wherein said gate means comprises an ANDgate operatively connected between said means for setting said minimumreciprocation cycles total and said warning means, and an ''''exclusiveOR'''' gate operatively connected between said means for registeringeach reciprocation cycle and said counter means so that said AND gatereceives a signal from said counter means so long as the totalreciprocation cycles counted by said counter means is less than the setminimum but does not pass said signal or unless and until a signal isalso received from said liquid flow sensing means, and said''''exclusive OR'''' gate receives signal pulses from said means forregistering each reciprocation cycle and passes samE on to said countermeans unless and until a signal is received from saidliquid-flow-sensing means.
 5. The apparatus according to claim 3 whereinsaid means for registering each reciprocation cycle is a microswitchcarried by said pump means.
 6. A method for monitoring potentialblowouts and lost circulation in a well wherein drilling fluid is pumpedinto the well bore, the improvement comprising determining minimum andmaximum tolerably amounts of drilling fluid to be pumped into said wellbore, measuring the amount of drilling fluid actually pumped into saidwell bore, sounding a warning if drilling fluid flows out of said wellbore before said set minimum amount of drilling fluid is pumped intosaid well bore, and sounding a warning if no drilling fluid flows out ofsaid well bore and said set maximum amount of drilling fluid has beenpumped into said well bore.
 7. The method according to claim 6 whereinsaid method is employed when removing tubing from the well bore.
 8. Themethod according to claim 7 wherein when tubing is being inserted insaid well bore, determining the amount of drilling fluid to be displacedout of the well bore by the amount of tubing to be inserted, measuringthe amount of drilling fluid actually displaced, and sounding a warningif more than the determined amount of drilling fluid is actuallydisplaced from said well bore.